Rock-boring machine.



. UNIT'T) vSTATs. i rArnNT ormoni. f

HEINRICH LoTTMANN, or BOCHUM, GERMANY. ROCK-"BORING MACHINE.

No. 806,128. I

Specic-ation of Letters Patent.

Patented Dec. 5, 1905.

Application led October 15, 1908. Serial No. 177,192.

.'To a/ZZ whom it may concern,.-

Beit known that I, HEINRICH FLorTMANN, a citizenof the German Empire,residing at Bochum, in the Province of Westphalia and Kingdom ofPrussia, Germany, have invented certain new and'useful Improvements inRock- Boring Machines, of which the following is a specification.

The valve-gears with self-movingvalve- `pistons of therock-boringmachines hitherto in use may be divided in two classes. In the one classthe valve-piston is'constructed as a so-called dierential piston, and inthe -other class ithas been tried -to construct this piston simplycylindrical in orderl to avoid the divisionof the valve-chamber whichwas nec` essary when differential pistons were used. All these systemsare based onthe principle to introduce air under pressure to thecontrolling device inthe proper moment, so that it may be-reversed,'andin the old systems also both admission-channels are reciprocally incommunication with the exhaust-channels.

These constructions require all of them more or less complicated devicesfor `being carried out practically, for if fresh air under pressure isadmitted on the one side for reversing the stroke the compressed air onthe other side must be exhausted, yor if this cannot be done ythecompression on'the one side must be overcome by the pressure on theadmission side.

The controlling device of the old systems also required specialconstructions, because besides the division of the compressed air orother driving means to both sides of theworking piston they had also togive the means for av means to act continually on both sides upon thevalve-piston, and I release the .same intermittently on oppositesides,'so that there will be overpressure, respectively, on the-one sideor on the other. This play of changing the pressure is done inmy case bythe working piston. It follows that While in the old designs the Workingpiston caused the admission of new compressed air it now causes theexhaust of the pressure medium on thatside toward v which thevalve-piston shall be moved. This mode of working allows varioussimplifications inthe construction of th`e valve-piston. Thus it neednot to be constructed so as to close the exhaust-channel of the cylinderand l form a special communication with a special exhaust-channel. Thisin my design is done by the working piston without the help of thevalve-piston. 1 By this I am not only en- 65 abledto design thevalve-piston as simple as possible, but the channels-,for the admissionofthe pressure medium and for exhausting the same canfbe made shorterthan in any other case. The reversinggmaybe done at any moment. .Theworking pistonat the end of its strokecloses the .exhaust-channelaso dthat no compressed air is wasted. In conse? fquence of this a certaincompression takes .-place 'on one side. of the .piston .which allows 75and enables a quicker return stroke of the piston, andtherefore themachine can Work at a higher speed than the machines of the old system.While these could only make live hundred to six hundred strokes per min-8 ute, the new machine will make about one thousand: I attain thisbyconstructing the machine and its valvefgear as shown on the accompanyingdrawings yin diagram form and as described hereinafter. v f

Figure 1 shows, a central longitudinal section through the cylinder andthe valve-chamber, with the Working piston at the right end. Fig. 2 is asimilar section showing. the working piston in its middle position, andFig. 3 90 .n

shows the same in its left position.

A Above the working cylinder A, carrying the working piston B, isarranged the valvecase C, containingthe valve-piston, having a reducedmiddle part Dand enlarged ends-D.

The compressed air or other driving means is admitted atE. Theadmission-channels to the piston F G and F G respectively distribute theair, as will be explained more particularly hereinafter. The valve-caseE is also in communication with the spaces J and J at both ends of thevalve-piston by the channels H land H, and the channels K and K,'whichcross each other, lead from the spaces J and J to the openings L and L.The exhaust IS air is carried away by exhaust-openings M andM',respectively. The valve-'piston D D is guided in the valve-box by itsenlarged heads D at both ends.- The length of the valve-piston is sogreatthat in its middle po- IIO sition the enlarged heads D'- cover theadmission-channels F G and F G', respectively, by

their inner edges, but that a small movement of the valve-piston only isrequired to form a communication between F and G and F and G',respectively. Supposing now that vboth the valve-piston and the workingpiston take the position indicated in Fig. l, then cornpressed air willpass through the channels F and Gr behind the working piston and willdrive it toward the left. When it has passed the exhaust-opening M',with the rear edge and also the opening L communicating With the spaceJ, Fig. 2, the used-up air can eX- haust freely and also the air in thespace .I can escape into the open air bythe channel K and the cylinderspace. In consequence of its 'mls inertia@ the piston will travelfarther toward the left and closes by its front edge the openings M andL', so that the air in front of it will be compressed, and when theopening L is closed the pressure of the air on the right side of thevalve-piston is greater than on the other side and presses thevalve-piston toward `the left, Fig. 3, and now the compressed air canenter to the front side of the piston B by the passages F G and willdrive lit to the right again, and so on.

It will be understood that the length of the Working piston must be solong as to cover at both end positions, Figs. 1 and 3, the channels M'and L and M and L', respectively, but that in the middle position of thepiston it must leave open for a short time only both systems ofchannels.

According to the description given above and with reference to thedevice shown, I claim as my invention- In valve-gears for engines drivenby compressed air and like driving mediums in combination with acylinder and a single working piston therein a valve-casing, avalve-piston located therein and having enlarged heads at both ends anda reduced middle portion, an admission-port, channels H, H leading fromsaid admission-port to spaces at both sides of the said valvepiston,other channels K, K

leading at opposite sides into the working' cylinder space andexhaust-openings M, M corresponding in position with the openings L, Llof the channels K, K into the working cylinder.

In testimony whereof I have aiiixed my signature in presence of twowitnesses.

HEINRICH FLOT'IMANN. Witnesses:

WILLIAM EssENWnIN, RUDOLPH LIEBER.

